Highly efficient and environmentally friendly silver powder preparation method

Abstract

This application provides an efficient and environmentally friendly method for preparing silver powder, belonging to the field of metal powders. The method includes first preparing a first reducing agent solution and a silver salt solution; mixing a suspension of nano-silver crystals with a nanoporous material and performing solid-liquid separation to obtain a solid powder; then mixing the solid powder with a second reducing agent solution to obtain solution B; finally, adding the first reducing agent solution and the silver salt solution dropwise to solution B to obtain a silver powder solution; and finally, processing to obtain silver powder. This application, by adding trace amounts of nanoporous material, provides sufficient growth sites for the reduced silver atoms, effectively reducing the agglomeration of silver powder particles. Furthermore, the nanoporous material is encapsulated within the micron-sized silver powder, without affecting the application performance of the silver powder. It replaces the use of organic dispersants in traditional liquid-phase reduction methods, reducing the types of raw materials and the difficulty of waste liquid treatment, thus reducing environmental pollution. The process is simple and efficient, suitable for industrial production.

Description

Technical Field

[0001] This invention relates to the field of metal powder technology, and more specifically to a highly efficient and environmentally friendly method for preparing silver powder. Background Technology

[0002] Silver powder, as an important metallic powder material, has wide applications in electronics, optoelectronics, and chemical engineering due to its unique physical and chemical properties. It is particularly favored by the market for its excellent tap density, dispersibility, and sphericity. Currently, the main methods for preparing silver powder include chemical reduction, physical methods, electrochemical methods, and gas-phase methods. Among these, chemical reduction is the most commonly used method due to its low cost and simple operation. However, traditional chemical reduction methods typically use large amounts of chemical reagents, causing environmental pollution and making it difficult to control the morphology of the prepared silver powder, thus failing to meet the requirements of high-end applications for silver powder morphology and performance. Therefore, traditional silver powder preparation methods often suffer from low efficiency, high cost, and environmental pollution, limiting their application in high-end fields.

[0003] With the continuous development of science and technology, silver powder preparation technology is also constantly improving. Future silver powder preparation technology will place greater emphasis on environmental protection, efficiency, and precise control. On the one hand, by improving the reagents used and reaction conditions in the chemical reduction method, the amount of chemical reagents used can be reduced, thus lowering environmental pollution. On the other hand, new physical and chemical methods will be developed to improve preparation efficiency and the precision of silver powder morphology control. Simultaneously, nanotechnology will be combined to prepare silver powder materials with special functions and properties to meet the needs of high-end fields.

[0004] A certain invention patent provides a method for preparing nano-silver powder, using spore-forming bacteria as fermenting microorganisms. Utilizing the fermentation action of these microorganisms, a large number of spores are produced during the diffusion, activation, and reproduction process. These spores exhibit good heat resistance during fermentation, resulting in nano-silver powder with relatively uniform particle size. The particle size of the nano-silver powder is controlled by manipulating the pore size of the polyoxymethylene (POM) to obtain nano-silver powder with good dispersibility. Although this method uses microbial raw materials, reducing the use of chemical reagents, the complex and inefficient microbial cultivation and preparation process, along with the large amount of raw materials required, leads to high costs, thus limiting its practicality and industrial application prospects.

[0005] Therefore, developing an efficient, environmentally friendly, and low-cost method for preparing silver powder has significant practical application value and market prospects. Summary of the Invention

[0006] In view of the technical problems existing in the background art, this application provides an efficient and environmentally friendly method for preparing silver powder, aiming to solve the technical problems of complex process, low preparation efficiency, large amount of chemical reagents used and difficult waste liquid treatment in the existing silver powder preparation.

[0007] This application provides an efficient and environmentally friendly method for preparing silver powder, comprising the following steps:

[0008] S1. Prepare the first reducing agent solution and the silver salt solution separately;

[0009] S2. Under constant temperature conditions of 60~90℃, the nano-silver crystal suspension and the nanoporous material are stirred and mixed to obtain solution A;

[0010] S3. Perform solid-liquid separation on solution A obtained in step S2 to obtain solid powder. Mix the solid powder with the second reducing agent solution to prepare solution B.

[0011] S4. The first reducing agent solution and silver salt solution prepared in step S1 are added dropwise to solution B in step S3. After the addition is completed, the mixture is stirred for 10 to 30 minutes to obtain a silver powder solution. The silver powder solution is washed, separated from solid and liquid and dried to obtain silver powder with a particle size of 0.5 to 5 μm, thus completing the efficient and environmentally friendly preparation of silver powder.

[0012] In the technical solution of this application embodiment, by adding nanoporous materials and mixing them with a nano-silver crystal suspension, the pre-adsorbed nanoporous materials provide sufficient growth sites for the reduced silver atoms, effectively reducing the agglomeration of silver powder particles. This replaces the use of polymeric organic dispersants in traditional liquid-phase reduction methods, reducing the types of raw materials and lowering the difficulty of waste liquid treatment, thereby reducing environmental pollution. Simultaneously, the nano-silver crystals regulate the size of the silver powder, resulting in well-dispersed, smooth-surfaced, and uniformly sized silver powder.

[0013] In some embodiments, in step S2, the pore size of the nanoporous material is 3-20 nm, the particle size is 20-150 nm, and the particle size of the nanosilver crystals is 5-15 nm. The nanoporous material is one of nanoporous metals, nanoporous alloys, or nanoporous non-metallic materials. In step S2, the mass ratio of the nanoporous material to the silver salt in the silver salt solution of step S1 is 1:(50-1000), and the mass of the nanosilver crystals in the nanosilver crystal suspension is 1:(1000-10000) of the mass of the silver salt in the silver salt solution of step S1.

[0014] In this embodiment, by limiting the size parameters of the nanoporous material and the silver nanocrystals, the silver nanocrystals can pre-adsorb onto the pores of the nanoporous material, providing dispersed generation sites for silver reduction. This also ensures that the nanoporous material is encapsulated within the micron-sized silver powder during its growth, preventing any impact on the powder's performance. This embodiment replaces the large amount of organic dispersant required in traditional chemical methods for silver powder preparation by adding a small amount of nanoporous material. After the reaction, the nanoporous material is encapsulated within the micron-sized silver powder, without affecting its application performance. Furthermore, there is no residue in the solution. The process is simple, environmentally friendly, and efficient, making it suitable for industrial production.

[0015] In some embodiments, in step S1, the concentration of the silver salt solution is 1~20 g / L, and the silver salt solution is a silver nitrate solution; the concentration of the first reducing agent solution is 5~10 g / L. The mass ratio of the reducing agent in the first reducing agent solution to the silver salt in the silver salt solution is 1:(0.5~2). In step S3, the concentration of the second reducing agent solution is 0.05~0.2 g / L, and the mass ratio of the reducing agent in the second reducing agent solution to the silver salt in the silver salt solution of step S1 is 1:(30~100).

[0016] In this embodiment, by limiting the amount of silver salt and reducing agent and the way the reducing agent is added, the preparation process of silver powder is made controllable, avoiding the generation of excessively large silver particles or unreduced silver salt residue, thereby ensuring the uniformity of the silver powder particles.

[0017] In some embodiments, the nanoporous material is nanoporous carbon. In step S4, the dropping rate is 5-20 mL / min, the stirring speed is 300-500 rpm / min, and the preparation environment is room temperature. The reducing agent in the first and second reducing agent solutions is one or a mixture of several of the following: sodium borohydride, triethanolamine, hydrazine hydrate, hydroquinone, hydroxylamine, ascorbic acid, sodium citrate, hydrogen peroxide, hydrazine sulfate, glucose, formaldehyde, and potassium iodide.

[0018] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, specific embodiments of this application are given below. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in this application will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort.

[0020] Figure 1 This is a microscopic electron microscope image of the silver powder prepared in Example 1 of this application;

[0021] Figure 2 This is a microscopic electron microscope image of the silver powder prepared in Comparative Example 1 of this application;

[0022] Figure 3 This is a microscopic electron microscope image of the silver powder prepared in Comparative Example 2 of this application. Detailed Implementation

[0023] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0025] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0026] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0027] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0028] Currently, the main methods for preparing silver powder include chemical reduction, physical methods, electrochemical methods, and gas-phase methods. Among these, chemical reduction is the most commonly used method due to its low cost and simple operation. However, traditional chemical reduction methods typically use large amounts of chemical reagents, causing environmental pollution and making it difficult to control the morphology of the prepared silver powder, thus failing to meet the requirements of high-end applications for silver powder morphology and performance. Therefore, traditional silver powder preparation methods often suffer from low efficiency, high cost, complex raw materials, and environmental pollution, limiting their application in high-end fields.

[0029] To address the technical problems of complex processes, low efficiency, large amounts of chemical reagents, and difficult waste treatment in existing silver powder preparation methods, this application provides a highly efficient and environmentally friendly silver powder preparation method. By adding a nanoporous material to a suspension of silver nanocrystals, the pre-adsorbed silver nanocrystals in the nanoporous material provide ample growth sites for the reduced silver atoms, effectively reducing the agglomeration of silver powder particles. This method replaces the use of high-molecular-weight organic dispersants in traditional liquid-phase reduction methods, reducing the types of raw materials and the difficulty of waste treatment, thereby reducing environmental pollution. Simultaneously, the silver nanocrystals regulate the size of the silver powder, resulting in well-dispersed, smooth, and uniformly sized silver powder. The addition of a small amount of nanoporous material in this application, after the reaction, encapsulates the micron-sized silver powder within the nanoporous material, without affecting the application performance of the silver powder, and leaves no residue in the solution. The process is simple, environmentally friendly, and efficient, suitable for industrial production.

[0030] The silver powder product prepared in this application has good dispersibility and uniform particle size, making it suitable for photovoltaic HJT cells. Moreover, the preparation method is simple, the ingredients are non-toxic, and it is easy to carry out industrial production.

[0031] For ease of explanation, the following embodiments use an efficient and environmentally friendly silver powder preparation method from an example of this application.

[0032] This application provides an efficient and environmentally friendly method for preparing silver powder, comprising the following steps:

[0033] S1. Prepare a certain amount of the first reducing agent solution and the silver salt solution respectively;

[0034] S2. Under constant temperature conditions of 60~90℃, the nano-silver crystal suspension and the nanoporous material are stirred and mixed to obtain solution A;

[0035] S3. Perform solid-liquid separation on solution A obtained in step S2 to obtain solid powder. Mix the solid powder with the second reducing agent solution to prepare solution B.

[0036] S4. Add the first reducing agent solution and silver salt solution prepared in step S1 dropwise to solution B in step S3. After the addition is complete, continue stirring for 10 to 30 minutes to obtain a silver powder solution. After washing, solid-liquid separation and drying, silver powder with a particle size of 0.5 to 5 μm is obtained, thus completing the efficient and environmentally friendly preparation of silver powder.

[0037] This embodiment adds a nanoporous material to a suspension of silver nanocrystals. The pre-adsorbed silver nanocrystals in the nanoporous material provide ample growth sites for the reduced silver atoms, effectively reducing the agglomeration of silver powder particles. This replaces the use of polymeric organic dispersants in traditional liquid-phase reduction methods, reducing the types of raw materials and the difficulty of wastewater treatment, thereby reducing environmental pollution. Simultaneously, the silver nanocrystals regulate the size of the silver powder, resulting in well-dispersed, smooth-surfaced, and uniformly sized silver powder.

[0038] Further, in some embodiments, in step S2, the pore size of the nanoporous material is 3-20 nm, the particle size is 20-150 nm, and the particle size of the nanosilver crystals is 5-15 nm. The nanoporous material is one of nanoporous metals, nanoporous alloys, and nanoporous non-metallic materials. In step S2, the mass ratio of the nanoporous material to the silver salt in the silver salt solution of step S1 is 1:(50-1000), and the mass of the nanosilver crystals in the nanosilver crystal suspension is 1:(1000-10000) of the mass of the silver salt in the silver salt solution of step S1.

[0039] In the technical solution of this application embodiment, by limiting the size parameters of the nanoporous material and the silver nanocrystals, the silver nanocrystals can pre-adsorb onto the pores of the nanoporous material, providing dispersed generation sites for silver reduction. This also ensures that the nanoporous material is encapsulated within the micron-sized silver powder during its growth, preventing any impact on the powder's performance. By adding a small amount of nanoporous material, the large amount of organic dispersant required for traditional chemical silver powder preparation is replaced. After the reaction, the nanoporous material is encapsulated within the micron-sized silver powder, without affecting its application performance. Furthermore, there is no residue in the solution. The process is simple, environmentally friendly, and efficient, making it suitable for industrial production.

[0040] Further, in some embodiments, in step S1, the concentration of the silver salt solution is 1~20 g / L, and the concentration of the first reducing agent solution is 5~10 g / L. The mass ratio of the reducing agent in the first reducing agent solution to the silver salt in the silver salt solution is 1:(0.5~2). In step S3, the concentration of the second reducing agent solution is 0.05~0.2 g / L, and the mass ratio of the reducing agent in the second reducing agent solution to the silver salt in the silver salt solution of step S1 is 1:(30~100).

[0041] In the technical solution of this application embodiment, by limiting the amount of silver salt and reducing agent and the way the reducing agent is added, the preparation process of silver powder is controllable, avoiding the generation of excessively large silver particles or unreduced silver salt residue, thereby ensuring the uniformity of the silver powder particles.

[0042] In some embodiments, the nanoporous material is nanoporous carbon. In step S4, the dropping rate is 5-20 mL / min, the stirring speed is 300-500 rpm / min, and the preparation environment is room temperature. The reducing agent in the first and second reducing agent solutions is one or a mixture of several of sodium borohydride, triethanolamine, hydrazine hydrate, hydroquinone, hydroxylamine, ascorbic acid, sodium citrate, hydrogen peroxide, hydrazine sulfate, glucose, formaldehyde, and potassium iodide; the silver salt solution is silver nitrate solution.

[0043] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0044] Example 1

[0045] This embodiment provides a highly efficient and environmentally friendly method for preparing silver powder, including the following steps:

[0046] S1. Prepare 0.5L of 8g / L ascorbic acid solution, stir and dissolve at a constant temperature of 25℃ to obtain the first reducing agent solution; prepare 0.5L of 10g / L silver nitrate solution, stir and dissolve at a constant temperature of 25℃ to obtain the silver salt solution.

[0047] S2. Under constant temperature of 80℃ and stirring at 300r / min, 0.02 g of nanoporous carbon (average particle size of 100nm and average pore size of 15nm) was added to 200 mL of nanosilver crystal suspension containing 0.001 g of nanosilver crystals (average particle size of 10nm), and stirred thoroughly for 8 h to obtain solution A.

[0048] S3. Perform solid-liquid separation on solution A obtained in step S2 to obtain solid powder. Mix the solid powder with 0.1 g / L ascorbic acid solution (second reducing agent solution) to prepare solution B.

[0049] S4. In a constant temperature environment of 25℃, at a stirring speed of 400 r / min, the first reducing agent solution and the silver salt solution prepared in step S1 are added dropwise to solution B in step S3 at a speed of 10 mL / min using a peristaltic pump. After the addition is completed, the mixture is stirred for 10 min to obtain a silver powder solution. The silver powder solution is then washed, separated from solids, and dried to obtain silver powder, thus completing the efficient and environmentally friendly preparation of silver powder.

[0050] Please see Figure 1 The image shown is a microscopic electron microscope image of the silver powder prepared in Example 1. As can be seen from the image, the silver powder has good particle dispersion, is mostly spherical in shape, has a smooth outer surface, and the particle size ranges from 0.5 to 5 μm. There are also no other obvious impurities.

[0051] Comparative Example 1

[0052] Comparative Example 1 provides an efficient and environmentally friendly method for preparing silver powder. The difference between Comparative Example 1 and Example 2 is that no nanoporous carbon is added in step S2. The rest is the same as Example 1 and will not be repeated here.

[0053] Please see Figure 2 The image shows a microscopic electron microscope image of the silver powder prepared in Comparative Example 1. It can be seen from the image that the silver powder has a wide particle size distribution, uneven particle size, and irregular morphology, exhibiting severe agglomeration. In addition to adsorbing silver nanocrystals and providing growth sites, porous carbon also acts as a dispersant in the reaction. In Comparative Example 1, no porous carbon was added, and the reduced silver atoms agglomerated during the growth process.

[0054] Comparative Example 2

[0055] Comparative Example 2 provides an efficient and environmentally friendly method for preparing silver powder. The difference from Example 1 is that in step S2, highly crystalline silver nanoparticles with an average particle size of 150 nm and no surface pores are used instead of silver nanocrystals. The rest is the same as in Example 1 and will not be repeated here.

[0056] Please see Figure 3 The image shows a microscopic electron microscope image of the silver powder prepared in Comparative Example 2. It can be seen from the image that the silver powder particles have poor dispersion and uneven morphology, and do not have a spherical morphology. The silver nanocrystal particles with an average particle size of 150 nm have reduced surface energy due to the increased particle size, and are not sufficient to provide growth sites for the silver atoms to be reduced subsequently, and cannot be adsorbed on the nanoporous carbon.

[0057] Example 2

[0058] Example 2 provides an efficient and environmentally friendly method for preparing silver powder. The difference from Example 1 is that nanoporous nickel is used in step S2. The rest is the same as in Example 1 and will not be repeated here.

[0059] Comparative Example 3

[0060] Comparative Example 3 provides an efficient and environmentally friendly method for preparing silver powder. The difference from Example 1 is that in step S2, nanoporous carbon with an average particle size of 300 nm is used. The rest is the same as in Example 1 and will not be repeated here.

[0061] Comparative Example 4

[0062] Comparative Example 4 provides an efficient and environmentally friendly method for preparing silver powder. The difference from Example 1 is that in step S2, nanoporous carbon with an average pore size of 50 nm is used. The rest is the same as in Example 1 and will not be repeated here.

[0063] Comparative Example 5

[0064] Comparative Example 5 provides an efficient and environmentally friendly method for preparing silver powder. Compared with Example 1, the difference is that step S2 is not performed. In step S3, nano-silver crystals, nanoporous materials and the second reducing agent solution are directly mixed to obtain solution B. The rest is the same as in Example 1, and will not be repeated here.

[0065] The silver powders prepared in Examples 1-2 and Comparative Examples 1-5 were tested for relevant properties, and the results are shown in the table below.

[0066] Table 1. Properties of silver powders prepared in Examples 1-2 and Comparative Examples 1-5

[0067]

[0068] As shown in Table 1, by comparing the results of the examples and comparative examples, it is evident that the preparation method using nanoporous carbon can effectively improve the morphology, particle size distribution, and conductivity of silver powder. In particular, Examples 1 and 2, by optimizing the use of nanoporous materials, produced silver powders with better spherical morphology and lower film resistivity, demonstrating the significant advantages of this method in improving silver powder performance. Comparative examples without added nanoporous carbon or with added nanoporous carbon of larger particle size and pore size exhibited irregular silver powder morphology and significantly decreased performance, further verifying the importance of nanoporous carbon in the silver powder preparation process. Nanoporous materials replace the use of organic dispersants in traditional liquid-phase reduction methods, reducing the types of raw materials and lowering the difficulty of waste liquid treatment, thus reducing environmental pollution. The process is simple and efficient, suitable for industrial production. Therefore, the silver powder preparation method proposed in this application has significant practical application value in improving silver powder performance.

[0069] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A highly efficient and environmentally friendly method for preparing silver powder, characterized in that, Includes the following steps: S1. Prepare the first reducing agent solution and the silver salt solution separately; S2. Under constant temperature conditions of 60-90℃, the nano-silver crystal suspension and the nanoporous material are stirred and mixed to obtain solution A; the pore size of the nanoporous material is 3-20nm, the particle size is 20-150nm, and the particle size of the nano-silver crystals is 5-15nm; the nanoporous material is one of nanoporous metal, nanoporous alloy, and nanoporous non-metallic material; the mass ratio of the nanoporous material to the silver salt in the silver salt solution of step S1 is 1:(50-1000), and the mass of the nano-silver crystals in the nano-silver crystal suspension is 1:(1000-10000) of the mass of the silver salt in the silver salt solution of step S1; S3. Perform solid-liquid separation on solution A obtained in step S2 to obtain solid powder. Mix the solid powder with the second reducing agent solution to prepare solution B. S4. The first reducing agent solution and silver salt solution prepared in step S1 are added dropwise to solution B in step S3. After the addition is completed, the mixture is stirred for 10 to 30 minutes to obtain a silver powder solution. The silver powder solution is washed, separated from solid and liquid and dried to obtain silver powder with a particle size of 0.5 to 5 μm, thus completing the efficient and environmentally friendly preparation of silver powder.

2. The efficient and environmentally friendly silver powder preparation method according to claim 1, characterized in that, In step S1, the concentration of the silver salt solution is 1-20 g / L, and the silver salt solution is a silver nitrate solution; the concentration of the first reducing agent solution is 5-10 g / L.

3. The efficient and environmentally friendly silver powder preparation method according to claim 2, characterized in that, The mass ratio of the reducing agent in the first reducing agent solution to the mass of the silver salt in the silver salt solution is 1:(0.5~2).

4. The efficient and environmentally friendly silver powder preparation method according to claim 1, characterized in that, In step S3, the concentration of the second reducing agent solution is 0.05-0.2 g / L, and the mass ratio of the reducing agent in the second reducing agent solution to the mass ratio of the silver salt in the silver salt solution in step S1 is 1:(30-100).

5. The efficient and environmentally friendly silver powder preparation method according to claim 1, characterized in that, The nanoporous material is nanoporous carbon.

6. The efficient and environmentally friendly silver powder preparation method according to claim 1, characterized in that, In step S4, the dropping rate is 5-20 mL / min, the stirring speed is 300-500 rpm / min, and the preparation environment is room temperature.

7. The efficient and environmentally friendly silver powder preparation method according to claim 1, characterized in that, The reducing agent in the first reducing agent solution and the second reducing agent solution is one or a mixture of several of the following: sodium borohydride, triethanolamine, hydrazine hydrate, hydroquinone, hydroxylamine, ascorbic acid, sodium citrate, hydrogen peroxide, hydrazine sulfate, glucose, formaldehyde, and potassium iodide.

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